I switch to different regions frequently and sometimes I forget to turn off my running instance from a different region. I there a way (a website provided by Amazon?) to display all the running instances regardless of region?
You can find all your running instances regardless of region and the cost they incur by going to the Account Activity page of your management console.
That dashboard is not real time and does not show one line per instance but it should help if you forget to turn off running instances.